1. Field of the Invention
The present invention relates to an image recording apparatus which prevents light exposure to a record area and non-record area on a photo-sensitive sheet when one or more image are recorded on one photo-sensitive sheet by a light modulated with an image signal.
2. Description of the Prior Art
A conventional apparatus of this type is shown in FIG. 1. A light output is usually a laser beam L emitted from a laser oscillator 1, and a light modulator 2, a collimator lens 3 and a rotating polygon mirror 4 are arranged along the path of the laser beam L. An f.theta. lens 6, a reflection mirror 7 and a beam detector 8 are arranged between the rotating polygon mirror 4 and a rotating drum 5.
The laser beam L from the laser oscillator 1 is modulated by the light modulator 2 which is driven by an image signal N supplied from a frame memory 9 in which the image signal is stored, and the modulated laser beam L is main-scanned by the rotating polygon mirror 4 through the collimator lens 3 to form a record image P on a photo-sensitive film F on the rotating drum 5 through the f.theta. lens 6. A portion of the laser beam L outside of an effective area of the record image P, which is transmitted through the f.theta. lens 6 is reflected by the reflection mirror 7 and directed to the beam detector 8 to generate a horizontal synchronization signal.
In this image recording apparatus, it is necessary to wrap the photo-sensitive film F around the rotating drum 5 before recording of the image P and remove the photo-sensitive film F from the rotating drum 5 after recording of the image P. During these operations, the laser beam L is cut off by the light modulator 2 but the cut off is not perfect and a very weak light is emitted. If one area on the photo-sensitive film F is repeatedly scanned by such light as the rotating polygon mirror 4 and the rotating drum 5 rotate, light exposure occurs on the photo-sensitive film F, among others, in the record area.
In an ideal light modulator, the output is zero if the input is zero. In actuality, however, the laser beam L from the light modulator 2 is not perfectly cut off due to, for example, the deviation of the signal even if the input to the light modulator 2 is zero, and hence light exposure cannot be entirely prevented.
In order to resolve the above problem, it has been proposed to improve the wrapping and removing mechanism so that the photo-sensitive film F does not pass through the main scanning line. However, this method requires a complex wrapping and removing mechanism.
In another method, the rotation of the rotating polygon mirror 4 is stopped during the wrapping and removing operations to stop the main scan of the laser beam L, and the laser beam L is oriented in a direction so as not to expose the photo-sensitive film F. In this method, however, the control of the rotating polygon mirror 4 is complex. Further, since the rotation of the rotating polygon mirror 4 is started after the photo-sensitive film F has been set on the rotating drum 5, time is wasted before the rotation of the rotating polygon mirror 4 is stabilized.
It may be necessary to completely cease or temporarily interrupt the recording of the image, in addition to the wrapping and removing periods of the photo-sensitive film F. In such non-record mode, the photo-sensitive film F may be exposed. The temporary interruption occurs in the following case. A multiformat camera type image recording apparatus for recording a plurality of images on one photo-sensitive sheet has the frame memory 9 for temporarily storing the input images. If the frame memory has a capacity large enough to store all images to be recorded, there is no problem. However, in order to save cost and space, such a frame memory is usually not used but a frame memory having a capacity which can store only a portion of the images to be recorded is used. When the frame memory becomes full, the image input is inhibited and the images inputted are recorded, and then the image input is again accepted and recorded at an appropriate timing of the rotating drum. In this method, the recording of the image must be temporarily stopped during the writing of the image input into the frame memory. If the light is exposed to the photo-sensitive sheet, among others, to the record area during the interruption of the recording, a serious problem arises.
When the recording operation is resumed from the interruption state, the scanning light may be in the record area in the main scanning direction. In this case, an unnecessary line is created as will be explained later.
In a medical application for which the apparatuses of this type are frequently used, even a small exposure is an obstacle to making a correct decision based on the recorded image. Accordingly, an apparatus which can completely prevent the exposure is required.